The invention is directed to a measuring instrument and a method for determining geometric properties of profile sections.
Measuring the three-dimensional arrangement of objects, for example of tubes and rods with different cross sections, is a frequently recurring problem in industrial measurement techniques. A frequent task is to measure tubes installed in automobiles, aircrafts, ships, submarines, laboratories, assembly lines and the like, and to determine their position in relation to a fixed coordinate system. Another frequently occurring task is adapting tubes to existing fittings. To accomplish this, an exact initial measurement of the position of these fittings and possible obstacles or passageways is required.
Different methods for measuring tubes are known in practice. A frequently used measuring instrument has a measuring fork with two intersecting light beams. The fork resides here on a measuring arm. Because the measuring arm has a defined origin in the coordinate system and because the position of the end of the measuring arm to which the fork is attached can also be determined, the spatial coordinates of the fork can be exactly determined. By suitable movement of the fork towards and away from the measure object, the spatial position of the tube and its diameter at the respective measurement location can be determined with suitable measurement software. The spatial positions of the tube fittings or obstacles can be measured additionally by mechanical scanning with an applied sensor tip. Positioning of the measuring fork relative to the measured object during the measurement process can be substantially supported with an oriented light beam.
With smaller tubes, it is also known to employ measurement banks with several video cameras. The geometry of the tubes can be determined from the images recorded with the video cameras by using 3-D software.
It is also known to measure tubes with surface scanners using suitable software. This measurement principle, however, is not suitable for shiny or strongly absorbing objects. This can be remedied by applying a dye or powder to the surface which, however, is rather time consuming.
U.S. Pat. No. 4,848,912 discloses use of two perpendicular light curtains with parallel light.